Specifically, Graham wants details on the chain of events leading to the stand down order issued by Africa Command to special operations forces stationed in Tripoli, according to Fox News.

The raid on the diplomatic outpost in Benghazi last September ended with the deaths of Ambassador Chris Stevens and three other Americans.

During a Senate defense committee hearing on the attack in February, Graham asked Dempsey if then-Africa Command chief Gen. Carter Ham ordered "a military asset in motion and someone told him to stand down?"

At the time, Dempsey replied: "No. In fact he was with us in the Pentagon."

During the exchange, neither man mentioned special operations forces stationed in Tripoli.

But Greg Hicks, the former top U.S. diplomat in Benghazi, told Congress this week that just as U.S. troops in Tripoli were about to depart for Benghazi, officials from Special Operations Command-Africa ordered the units to stand down.

The Pentagon maintains those special forces troops in Tripoli would not have arrived in Benghazi in time to thwart the attack.

“Clearly ... our chairman of the Joint Chiefs's rendition that no one was told to stand down is now in question," Graham told Fox News on Friday.

Dempsey's spokesman Col. David Lapan told The Hill that the four-star general "stands by his testimony" delivered to the Senate defense panel in February.

Graham's questioning of Dempsey's testimony is only the latest GOP accusation of a cover-up by the Obama administration on the Benghazi attack.

Republicans have accused the Obama administration of changing the “talking points” about the attack for political gain in the heat of the 2012 presidential election.

Republicans say the talking points used by U.S. Ambassador to the United Nations Susan Rice intentionally downplayed the al Qaeda connections and falsely blamed the attack on a spontaneous protest.

Only later did U.S. military and defense officials acknowledge the attack was the work of Islamic militant groups based in western Libya.

However, the Pentagon recently denied a request by House Armed Services Committee chief Rep. Buck McKeon (R-Calif.) for classified materials related to Benghazi.

While the Defense Department did issue an unclassified timeline about the attack, it did not produce a classified timeline or report on Benghazi that could be provided to lawmakers, the DOD said in a letter to McKeon.

The only work Pentagon officials did was prepare "draft working documents" for military and intelligence officials to brief lawmakers on the attack and subsequent American response, according to the letter, sent Wednesday.